Devices for centralizing casing in boreholes



i March Filed May 12, 1952 3, 1956 A. E. ATKINSON DEVICES FORCENTRALIZING CASING IN BQREHOLES 4 Sheets-Sheet 1 6 o o I: v l l 2a 5 /74 n 0 y Z I I\ 9 1 6 o o 6 I! 11 March 13, 1956 A. E. ATKINSON 2,733,019

DEVICES FOR CENTRALIZING CASING IN BOREHOLES Filed May 12, 1952 4Sheets-Sheet 2 March 13, 1956 A. E. ATKINSON DEVICES FOR CENTRALIZINGCASING IN BOREHOLES Filed May 12, 1952 4 Sheets-Sheet 3 March 13, 1956A. E. ATKINSON 2,738,019

- DEVICES FOR CENTRALIZING CASING IN BOREHOLES Filed May 12, 1952 4Sheets-Sheet 4 witha" sin J I i J en BOREHOLES Edwaid Atkinson; Essen;England Application'May 1 2 1 9 2 S eri aI N ot 287,3 I Claims priority,application Great Britain Mnyza la sr I 1 2 oi. 115L241) inventionrelates to" devices for centralizingcasreholes in conjunction was: welldrillinfi and like op tion's"; or the kind comprising: an annular seriesof sprin s connected at their ends t6 spacedrings are adapted to" befitted to the exterior ofthe easing or pipe so that the bowed portionsof the springs can iig'dge the wall of the borehole.

. In patent application No. 197,698, filed November 11, 1950} new PatentNo". 2,680,488,- there is desdribed a: de-

er the above in which the bowed springs are connected to theif end ringsin such a: mannen'that the sewer s'fi'ng portions can'- be initiallystressed to increase fs'lsifahlce to lateral loads, the springs beingfiild ripen tire casing or pipe for this purpose.- Itis 6f the dbjctsorthe present invention t6 provide an device or the describedwhich affordsa freedom of relative rotation between use device and Hi" 6:

-asiiig or pipe. Another object is to provide an d'v s which can beemployed in cdnjunlction is sto ringor equivalent means only} whichgitiidinal lost motion be ween the device and tiff to the sin or pipe.

bjec't of the invention is to provide a; device referred to ahove inWhich initial stressing of the sewer springs is effected by anengagement or ful- 5f 2; pait or parts of the springilpon one or both ndriiig's.

M dbjet is to" provide a device according to the fii dedin'g paragraphin which one 6r both of the end rings is extended axially to provide acontinuous peiiplabial portion upon which the springsare ngaged. Thesprings may be similar to those described in the Q50? mentioned patentapplication but with the outwei dly bent portions omitted. 1 I

A fiirther object is to provide a device acgordiiig to either of the twopreceding paragraphs, applied to 5 casing or pipe having a single stopring or equivalent stop lugst In the accompanying drawings;

Figure l is a side elevation of a 'iitraliiihg' device constructed andarranged according to the invention;

Fibre 2 is a side elevation, partly in s'eti'dn, to an eniai'g'e tile orone or the endrings of the device;

, Figure 3 is an end view of the device, showing the posinan 6f the ringwhen openecl out;

guns 4 is "a side elevation of a modified roan of end Ifigur 5 is an endview of the ring of Figure 4;

Figure 6 is aside elevation of the separated ring halves joiiiing; gure7 is an end view of the ring halves of Ei'gureh; Figure 8 is a sectiontaken on the line 8-8 ofFigure 5; Figure 9 is an end view of a furthermodified form of end ring; a

a Figure 10 is a side elevation of the end ring of Figure 9.

. In carrying the invention into effect according to one "convenientmode as illustrated in Figures to 3, "the 'device comprises an annularseries of bowed springs 1 se United States 2,738,019 Pti'tented- Mar.13, 19.56

. 2" c'u'reds at their endsto spaced rings 2 whichare' fitted to theexteriorofithe bore' hole casin-g. 3 so that thebowed portions oi the;springs can engage the wall of. the bore hole. Each. of the springs 1 isformed.- asdescribed: in

patent application No. 191,698 of Novem-ber 27', 1950,

but with the outwardly bent portionsemitted. Each spring comprises abowedportion having at eachend an intermediate or parallel portion-4jbined to an end or extension portion 5- having: at itsend a. turnedout. lug 6. spring is 'formed'so that. when. infree condition anddisconnected from the endrings the integralspring extensions 5: will beinclined outwardly with respect to a plane surface upon which the springislaid. position is: shown in chain dotted lines in Figure I for one endof thespr ing. Such form ation results-in the spring being stressed whenthe said extension portions at the opposite ends ofeachspring arebrought into aligned relation when the spring is mounted on the rings.The end rings 2 are oi greater axial length than the ringsdescribed inthe above mentioned patent application and have a substantiallyperipherally continuous portion 7 at their inner ends uponwhich theintermediate portions 4' of the springs are engaged when the spring andis secured to the ring, thereby affording a fulcrum forthe stressing of.the spring. Each of the endrings is split and is formed by a pair ofhalf rings 2a and 2b connected by hinges 8. By removing one of the hingepins the ring can be opened as shown by broken lines in- Figure 3 forremoval from the casing. Each ring or ring half is formed with a seriesof axially extending rectangular openings 9 in which the spring ends.can be received. Lugs or bridge portions 10 of shallow channel shapeextend across the said openings towards the outer end of the ring. toleave a narrow slot at said end to receive the turned out lugs 6 at thespring ends. The lugs or bridge portions 10 may be formed integrallywith the rings or may be welded thereto as may be desired. Stop members11 are formed, or welded, on the ring at the outer end of each ofsaidslots to form an abutment for the spring end. The arrangement is suchthat when the springs are connected to the rings and'assembled on thecasing vor pipe 3, each spring bow is initially stressed by thedisplacement of the spring extension portions 5 :by engagement ot theintermediate portions 4 with the end rings to force such portionsof.thesprings apart. The inner edges of the bridge pieces 10 may beehamfered as shown at 12 if desired to facilitate insertion of thesprings. When using such an arrangement, there .is no engagement betweenthe springs and the casing or pipe so that the latter is free to turninside the device and is not subject to frictional drag.

.-A centralizing device as described above can be used in conjunctionwith the usual pair of casing stop rings such as are illustrated in thepatent application referred to previously but if desired a single stopring or its equiva lent may be employed. A single stop ring is shown at13 in Figure -1. Instead of a stop ring, two or more lugs may be weldedor otherwise .secured to the casing or pipe so that they serve as theequivalent of a ring. The use of such stop lugs is permissible with acentralizing device as described above by reason of the end rings beingperipherally continuous at their inner ends, i. e. there are no openingswithin whichsuch stops could be accidentally engaged. When using asingle stop, lost motion is afforded between the casing and the device,and when movement of the casing is reversed it will travel the distancebetween the end rings before engaging the device. This may be anadvantage in some circumstances since the device will thereby be jarred.Also when setting or'picking up casing slips for the addition of a newlength of casing the small movement of the casing involvedwill notdisplace the centra'lizing device.

' Instead of joining the ring halves by hinge members and pins aspreviously described, a modified form of connection as illustrated inFigures-4 to 8 may be employed. Two ring halves 14 and 15 are providedand these may conveniently be formed from sheet metal of suitablethickness. The ends of the ring half 14 are each formed with anoutwardly and rearwardly extending fold portion 16 the ends of which arecut away at 17 so that this fold portion is of shorter longitudinalextent than the ring. The ends of the ring half 15 are each formed withan inwardly and rearwardly directed fold portion 18 which is radiallyoffset at 19. The disposition of the two folds 16 and 18 is such thatthey can be interengaged as shown in Figure 5 to form a complete ring.The fold portion 18 extends the full length of the ring and the outerportions 20 of the said fold are partially separated from the main partthereof by slits or saw cuts 21, the part 22 between the slits beingequal in length to that of the outward fold 16. The arrangement is suchthat after the ring halves have been assembled as shown in Figures 4 and5, preferably by a longitudinal sliding of the two halves, the portions23 lying outside the slits 21 can be flattened down, as for example byhammering, so that they lie adjacent the ends 17 of the short foldportion 16 and thereby secure the ring halves against relativelongitudinal displacement. Each ring half is provided with openings 24,bridge portions 25, and stop members 26 as described in the previousexample for receiving the springs, one of which is indicated by brokenlines at 27 in Figure 4. The ends of the bridge portions may bechamfered at 28 (Figure 8) to facilitate insertion of the springs. Thearrangement is otherwise as described in the previous example.

In a further modified construction as shown in Figures 9 and 10, thering halves 29, 30 have their adjacent ends formed with similarly shapedoutwardly folded portions 31 and 32. These folded portions are engagedand connected by a pair of strips 33 which are of C-section as shown inFigure 9. The strips 33 have slits or saw cuts 34 in their outer sidesleaving end portions 35, and the outward folds 31, 32 of the half ringedges are shorter than the ring so that they extend only to the slits34. When the ring halves are assembled by sliding the C-strips 33 overthe fold portions as shown, the end portions 35 of the strips areflattened as by hammering so that the connection is secured. Thearrangement is otherwise as described in the previous examples, and oneof the springs is indicated at 36 in broken lines in Figure 10.

Itwill be appreciated that with the construction according to theinvention, it is not possible readily to disengage the bowed springsfrom the end rings once they have been assembled thereon, since by thevery nature of the prestressed springs, special tools are necessary toforce the spring ends into the ring openings and under the bridgeportions and to force the springs longitudinally until their turned outlugs engage in the slots, the tool being then removed; When assembled,the blades and end rings form a unitary whole, similar to the knownriveted cen tralizers, irrespective of whether the centralizer is on thecasing or not. Thus the dismantling of an assembled unit would be anextremely diflicult operation, but is not normally required. If desiredby the user, the end rings and springs can be dispatched separately forassembly on site.

It will be understood that the improvement is not restricted to theabove examples, since the details of con struction of the end rings andof the mode of connecting the springs thereto may be variously modified.Also if desired, the end rings may be of continuous or integralconstruction instead of split as previously described.

' Iclaim:

1. A device for centralizing casing in boreholes of the type having aseries of centrally bowed leaf springs that have end portions by whichthey are secured to spaced end rings and assembled therewith about theexterior of a bore hole casing with their bowed portions outwardlydirected, particularly characterized by means on the end rings foranchoring the springs thereto and further characterized by the springsbeing formed so that when in unassembled condition the said end portionswhich are intended to be secured to the anchoring means and to beengaged by the end rings, respectively, lie in planes which are inclinedoutwardly relative to the planes which they occupy when secured to theend rings, such that when the springs are assembled upon and secured tothe rings the portions of the springs connecting the said end portionsto the bowed portions will engage the outer surfaces of the end ringsthereby fulcruming the engaging portions thereof upon the end ringsinwardly of the anchorage points to increase the outward bowing of thesprings and thereby increase the resistance of said bowed portions tolateral loads.

2. A device according to claim 1, in which the springs are fulcrumedupon the exterior of each end ring which is substantially continuousperipherally.

3. A device according to claim 1, in which each of the springs comprisesa bowed portion and two end portions, each end portion including aterminal portion connected to the ring and joined to an intermediateportion which in the assembled condition of the springs liessubstantially parallel to the ring axis and is engaged and fulcrumed onthe end ring.

4. A device according to claim 1, in which each spring end has anoutwardly projecting lug and the end rings have openings within whichthe said lugs are engaged, and an intermediate portion of each spring isfulcrumed upon a peripheral portion of the said ring.

5. A device according to claim 1, in which the end rings have axiallyextending openings for receiving the spring ends and each opening has abridge piece extending across it to afford a slot at one end thereof,and each spring end has an outwardly extending lug which in theassembled condition of the springs is engaged within the slot with theadjacent spring portion lying beneath the bridge, thereby affording adetachable spring anchorage.

6. A device according to claim 1, in which the end rings have axiallyextending openings for receiving the spring ends and each opening has abridge piece extending across it to afford a slot at one end thereof,and each spring end has an outwardly extending lug which in theassembled condition of the spring is engaged within the slot with theadjacent spring portion lying beneath the bridge, and stop members areprovided on the end rings at the outer end of each slot to form anabutment for the spring end, thereby affording a detachable springanchorage.

7. A device according to claim 1, in which the end rings arelongitudinally divided.

8. A device according to claim 1, in which the end rings arelongitudinally divided and joined by a pair of hinged members and pinswhereby the assembled springs are held in strained condition when thesaid rings are opened for placing over the casing.

9. A device according to claim 1, in which the end rings arelongitudinally divided and the ring parts are secured together by foldedjoints.

10. A device according to claim 1, in which the end rings are dividedlongitudinally, and the adjacent ends of the ring parts haverespectively inward and outward folds constituting an interfitted joint,one of the mating folds being shorter than the other fold and beingoverlapped by the other fold, the said overlapping parts being capableof deformation as by hammering to secure the joint.

11. A device according to claim 1, in which the end rings are dividedlongitudinally and the adjacent ends of the ring parts have respectivelyinward and outward folds constituting an interfitted joint, one of themating folds being shorter than the other fold and being overlapped bythe other fold, and slits being provided in the overlapping portions toseparate said portions from the main I part of said fold wherebydeformation of said overlapping I portions as by hammering to secure thejoint is facilitated.

5 12 A device according to claim 1, in which the end rings arelongitudinally divided and the adjacent ends of the ring parts haveopposed folds and a C-section strip is engaged with said folds toconstitute an interfitted joint which is capable of being deformed as byhammeringto 5 secure the connected folds.

References Cited in the file of this patent UNITED STATES PATENTSHartman Aug. 25, 1931 Dennie Nov. 29, 1932 Crawford M July 8, 1941 BakerMar. 27, 1951 Clark Aug. 5, 1952 Atkinson June 8, 1954

